The present invention generally relates to electrical connectors, and more particularly, to electrical connectors for mating circuit cards and the like with frames, racks and other chassis for receiving such circuit cards.
Any of a variety of systems have been developed for receiving a series of circuit boards (i.e., circuit cards) in a frame, rack or other chassis. To this end, the frame, rack or receiving chassis is provided with a series of electrical connectors capable of mating with corresponding structures provided on the circuit cards. The resulting connections then operate to supply each circuit card with power for its operation, and to permit the exchange of data and any necessary operating signals.
In practice, it is generally necessary to combine a relatively large numbers of circuit cards in a single system to achieve a desired result. Over time, the need will arise to service the circuit cards, for example, to replace a circuit card which has become defective, to make an exchange with a circuit card having modified or upgraded capabilities, or to add a circuit card to or delete a circuit card from the overall system.
During such servicing procedures, it was traditionally necessary to remove power from, or “power down” the circuit cards to be serviced (removed or replaced) to protect the electrical systems associated with the circuit cards being serviced and/or other circuit cards associated with the system. This would often require a large number of circuit cards to be powered down to perform a desired servicing operation. This could, in turn, lead to a significant loss of function (system downtime) during the servicing procedure.
To minimize such losses of function during a desired servicing operation, so-called “hot plug” systems were developed. Such systems allow individual circuit cards to be addressed, and powered up and down from a central control unit. This then allows the individual circuit cards to be removed, replaced and/or added to the system without first having to take the system, or substantial portions of the system, off-line (i.e., powered down). As a result, portions of the system other than those requiring service can continue to operate during the servicing procedure, in this way minimizing losses of overall system function during such servicing. For this reason, hot plug technology has become an industry standard solution for providing users with increased system availability (reduced system downtime) and enhanced serviceability in various computing environments.
In operation, hot plug technology allows a single circuit card, for example, a PCI adapter card, to be isolated from the remainder of the system by isolating the PCI slot which is to receive the PCI card from other devices associated with the system. Isolation of the PCI slot includes the powering down of the (single) PCI slot, allowing the removal and/or insertion of a PCI card, and protection of the remaining elements of the system from potentially adverse electrical effects of the PCI card exchanges being made. The result is that the identified PCI card can be removed and/or inserted without interrupting the ongoing operations being performed by the remainder of the system.
Although such operations permit individual circuit cards to be removed and replaced while minimizing losses of function (system downtime) during the servicing procedure, it remains necessary to physically remove and insert the circuit cards during such servicing. Depending on the configuration of the frame, rack or chassis which receives the circuit cards, this can lead to some practical disadvantages.
For example, a common high availability solution for minimizing system downtime in industry-standard servers uses hot plug technology in conjunction with a mounting rack for receiving plural PCI adapter cards. Slots for receiving the PCI adapter cards are defined by electrical connectors which are physically connected to the rack, and which include a series of pins extending along opposing sides of the slot defined by the electrical connector for establishing electrical connections with a corresponding series of pads provided on the surfaces of the PCI adapter cards (i.e., along the “card edge”). The edge of the PCI adapter card having the series of pads can then be frictionally engaged within the slot of one of the electrical connectors, and between the series of pins, establishing necessary electrical connections with the electrical connector and the remainder of the system, and retaining the PCI adapter card in desired position.
To remove a PCI adapter card, the card is grasped (by hand or using a tool) and pulled from the electrical connector. To install a PCI adapter card, the edge of the PCI adapter card having the series of pads is aligning with the slot defined by the electrical connector, and the aligned card edge is inserted into the slot so that the pads on the card edge are engaged by the pins of the electrical connector.
Depending upon the orientation of the PCI adapter card and the electrical connector (horizontal, vertical, etc.), and the structural elements comprising the rack, access to the PCI adapter card can at times be limited. Consequently, while hot plug technology can operate to temporarily deactivate a PCI slot which is to be accessed, the amount of time and difficulty in physically accessing the PCI adapter card remains limited by the relative inconvenience of accessing a particular slot.
To help minimize this inconvenience, the PCI adapter cards and the slots (connectors) which are to receive them are often grouped together in a so-called “module box” which is removably mated with the rack. The module box can then be pulled from the rack to expose the PCI adapter cards it contains for servicing. In conjunction with hot plug technology, the PCI adapter cards associated with the module box are isolated, for servicing, while the remainder of the system remains powered.
While this facilitates access to the PCI adapter card which is to be serviced, this then leads to a corresponding disadvantage that the remaining PCI adapter cards associated with the module box are also deactivated when the module box is removed from the rack, giving rise to a potential loss of function. Consequently, the need remains for an electrical connector which can receive circuit cards in a manner which permits individual circuit cards to be accessed for service, independently of other circuit cards associated with the system and without interrupting operations of the other circuit cards associated with the system.
Irrespective of the configuration of the rack (frame or chassis) which is used to receive the PCI adapter cards, the frictional engagement which is maintained between the card edge and the electrical connector will, over time, tend to cause these components to wear as a result of repeated servicing operations. Consequently, the need remains for an electrical connector which can receive circuit cards in a manner which reduces the amount of friction developed between the engaged card edge and the electrical connector, to increase the overall durability and service life of both the card edge and the electrical connector.